Characterization of ouabain receptor in neuronal tissue: Evidence for endogenous ouabain-like compound

This study shows that [³H]ouabain binds specifically to a single, saturable binding site located on rat brain membranes with an affinity constant of 6.21 X 10^-8 M. As expected from studies on the mechanics of the Na⁺,K⁺-ATPase, sodium increased while potassium and lithium decreased ouabain binding. The occupation of other neurotransmitter receptors did not affect [³H]ouabain binding. Based on its ability to compete with [³H]ouabain binding and to inhibit Na⁺,K⁺-ATPase, it is suggested that that rat brain extract contains an endogenous ouabain-like compound. The results are discussed with respect to the possibility that the ouabain receptor is a physiological regulatory site of the Na⁺,K⁺-ATPase activity.